In the United States, many coronary artery bypass graft (CABG) procedures performed on patients annually. Each of these procedures may include one or more graft vessels which are hand sutured. Until recently, coronary artery bypass procedures have been performed with the patients on cardiopulmonary bypass while the heart is stopped with cardioplegia and the surgery is performed on an exposed, stationary heart.
The vast majority of CABG procedures performed currently are accomplished by opening the chest wall to gain access to the coronary vessels. Through the use of heart lung bypass machines and a drug to protect the heart muscle, the heart is stopped and remains still during the procedure. In this setting, the surgeon has ample time and access to the vessels to manipulate hand suturing instruments such as forceps, needle holders and retractors.
However, with increasing costs of hospital stays and increased awareness by patients of other minimally invasive surgical procedures interest in developing a minimally invasive CABG procedure is increasing hospitals need to reduce costs of procedures and patients would like less post-operative pain and speedier recovery times.
With an increased incentive to reduce costs, there is a renewed interest in redesigning cardiothoracic procedures. A few pioneering surgeons are now performing minimally invasive procedures whereby the coronary artery bypass is performed through a small incision in the chest wall. There are some surgeons that believe that the best way to perform a minimally invasive coronary artery bypass procedure is to perform the procedure on a beating heart, i.e., without heart-lung bypass and cardioplegia. This minimizes the time it takes to perform the procedure and reduces the cost of the operation by eliminating the heart lung bypass machine.
In the case of minimally invasive procedures on a beating heart, the surgeon starts by making a mini-thoracotomy between the fourth and fifth ribs and, sometimes, removing the sternal cartilage between the fourth or fifth rib and the sternum. The space between the fourth and fifth ribs is then spread to gain access to the internal mammary artery (IMA) which is dissected from the wall of the chest. After dissection, it is used as the blood supply graft to the left anterior descending artery of the heart (LAD). Below the IMA lies the pericardium and the heart. The pericardium is opened exposing the heart. At this point, the LAD may be dissected from the fissure of the heart and suspended up with soft ligatures to isolate the artery from the beating heart.
Typically, a special retractor gently applies pressure to the heart muscle to damp movement at the LAD. A small arteriotomy is performed in the LAD and the graft IMA is sutured to the LAD.
Traditionally, to gain access to the cardiac vessels to perform this procedure the sternum is sewn in half and the chest wall is separated. Although this procedure is well perfected the patient suffers intense pain and a long recovery.
Until recently all bypass graft procedures have been performed by hand suturing the tiny vessels together with extremely fine sutures under magnification. The skills and instruments required to sew extremely thin fragile vessel walls together have been perfected over the last twenty years and are well known to the surgical community that performs these procedures.
FIG. 1 shows a conventional anastomosis using hand-sutures, in which coronary artery 10 and graft vessel 12 are connected in side-to-side fashion One end (13) of vessel 12 is tied closed, and the side wall of vessel 12 near this closed end is to be attached to artery 10. The opposite end of vessel 12 (not shown) is to be attached to an aorta or IMA. In typical cardiopulmonary bypass procedures, one end of a graft vessel is grafted to a coronary artery (at a “distal” graft site) and the other end of the graft vessel is grafted to the aorta (at a “proximal” graft site). FIG. 1 shows a distal graft site. An incision 14 is made in artery 10 and a corresponding incision 16 is made in graft 12. The surgeon aligns the incisions and hand-sutures the aligned edges of the incisions together using sutures 18 and 20. Hand-suturing can also be used to perform an end-to-side anastomosis, in which an open end of the graft vessel is aligned with an incision in the sidewall of another vessel (e.g., an aorta) and the aligned tissue is hand-sutured together. The present invention can be used to perform either end-to-side or side-to-side anastomosis without hand-suturing.
There is a need (which is addressed by the present invention) for methods and apparatus useful for performing anastomosis during CABG surgery on a beating heart. When performing anastomosis during such surgery on a beating heart, use of hand-suturing to attach the graft vessel is very imprecise due to the translation of movement from the beating heart to the suspended artery. This motion may cause imprecise placement of the suture needles. Any imprecise placement of the sutures may cause a distortion of the anastomosis which may cause stenosis at this junction. The sutures used for this procedure are extremely fine (0.001″ in diameter) and are placed less than 1 mm apart.
As one can imagine it is difficult enough to place suture needles the size of a small eyelash into a vessel wall with placement accuracy of better than 1 mm. To accomplish this feat of precision on a moving target is extremely difficult. To make matters worse, the site is often bloody due to the fact that the heart has not been stopped. During beating heart surgery, the surgeon can attempt to minimize the deleterious effects of the beating heart motion by using suspension or retraction techniques, but it is impossible to isolate all such movement (and attempts to minimize the motion can damage the vessel being restrained or cause myocardial injury). Even when performing anastomosis in an ‘open chest’ surgical setting in which the surgeon has adequate access and vision of the surgical site to manipulate the anatomy and instruments, it is difficult to perform the hand-suturing required in traditional methods. When performing anastomosis in a minimally invasive procedure access to (and vision of) the site is more limited and the hand-suturing is more difficult.
If the sutures are not placed correctly in the vessel walls, bunching or leaks will occur. During a minimally invasive procedure this is disastrous, usually resulting in the conversion to an open chest procedure to correct the mistake. Any rough handling of the vessel walls is detrimental as inflammation can cause further postoperative complications.
An anastomosis must seal without leaking to prevent exsanguination. Therefore, any anastomosis technique which does not require hand sutures must provide a leak free seal in a very confined space, while providing proper flow area in the vessel after healing is complete.
Although minimally invasive CABG procedures are taking place now with hand-sutured anastomosis they require superlative surgical skills and are therefore not widely practiced. There is a need for methods and apparatus which permit the forming of a precise anastomosis without requiring the stopping of a beating heart, during either minimally invasive or open chest surgery, and without requiring hand suturing.
Several techniques have been proposed for performing anastomosis of blood vessels. However, the prior art techniques often require the vessels to be severely deformed during the procedure. The deformation may be required to fit the vessels together or to fit a vessel to an anchoring device.
For example, some prior art anastomosis techniques have used rigid rings to join two vessels together. In one such technique (indicated by FIG. 2), rigid ring 30′ is positioned around the edges of an incision in the sidewall of artery 31 in a manner that inverts the tissue near the incised edges (by everting the tissue) to expose the inside lining (intima) of the vessel walls. The incised edges can be anchored on a flange (not shown) on ring 30′. Rigid ring 30″ is positioned around the open end of graft vessel 31 in a manner that inverts the tissue at the open end (by everting the tissue), thereby exposing the intima of vessel 31. Then, rings 30′ and 30″ are moved into alignment with each other and fastened together (e.g., by a clamp) so that the intima of the vessels are clamped together in contact with each other.
In another such technique (indicated by FIG. 3), rigid ring 30 is positioned around the open end of vessel 33 in a manner that inverts the tissue at the open end (by everting the tissue), thereby exposing the intima of vessel 33. Then, the open end of vessel 34 is fitted over (and fastened to) the ring-containing end of vessel 33.
However, it may be undesirable to simply slit side-wall tissue of a vessel and pull the incised edges through a ring (as in FIG. 2) to anchor them on a flange (or to invert and pull tissue at the end of a vessel over a ring as in FIG. 3). Pulling or stretching the vessel walls can produce an unpleasant and unexpected result. Vessel walls are made of tissue fibers that run in the radial direction in one layer and the longitudinal direction in another layer. In addition the elasticity of the tissue fibers in the longitudinal direction is greater than those that run radially. Therefore, the tissue will not stretch as easily in the radial or circumferential direction and results in a narrowing or restriction when pulled or stretched in the prior art devices. Vessel walls also have a layer of smooth muscle cells that can spasm if treated harshly. Such manhandling will result in restrictions and stenotic junctions because the vessel walls will react poorly to being treated in such a rough manner and the stretching of the vessel wall will telegraph up the vessel wall due to the high radial stiffness of the vessel structure, causing restrictions and spasms in the vessel wall.
Additionally, prior art methods and apparatus for anastomosis without hand-suturing do not adequately ensure hemostasis to avoid leakage from the anastomosis junction under pressure, and they attempt to accomplish hemostasis through excessive clamping forces between clamping surfaces or stretching over over-sized fittings.
In order to effect good healing, healthy vessel walls must be brought into intimate approximation. This intimate approximation can be accomplished by the skilled hands of a surgeon with sutures. A vascular surgeon is taught how to suture by bringing the vessel edges together with just the right knot tightness. If the edges are tied too loosely, the wound will leak and have trouble healing causing excessive scar tissue to form. If the edges are tied too tightly, the sutures will tear through the delicate tissue at the suture hole causing leaks. The key is to bring the edges together with just the right amount of intimate approximation without excessive compression.
Conventional junctions that include rings are anatomically incorrect both for blood flow and for healing. A well made anastomotic junction is not made in a single plane and should accurately follow blood vessel geometry. The junction is more of a saddle shape, and the cross section is not necessarily a circle. The junction where the vessel units join is not a constant cross section angle, but an angle that varies continuously throughout with respect to any linear reference. In addition, the length of the junction should be many times the width of the opening in order to assure a low blood flow pressure gradient in the junction and to assure a proper flow area. In fact, the best results are obtained if the confluence area is actually oversized. The prior art junctions do not account for such flow characteristics and parameters and are thus deficient. There is a need for an anastomotic technique which can establish proper flow characteristics and parameters and that accurately preserves blood vessel geometry, specifically the plural planar nature in which the junction occurs. Furthermore, most anastomoses are made between vessels that are not similar in size. It is therefore necessary to provide a means and method which allow for the accommodation and joining of dissimilarly sized vessels.
After attachment of a graft vessel by anastomosis, the supply vessels grow in diameter to accommodate their new role in providing oxygenated blood to the heart. Therefore, there is a need to provide a junction that will accommodate any increase in the dimension of the graft vessel size. With a rigid ring that is a singular circular cross section of the graft, the fitting does not allow the vessel to provide this increase in flow as the vessels expand to meet the needs of the heart muscle. Still further, the inside lining of the vessel walls (intima) should make contact with each other (for a variety of reasons). The walls of the joined vessels must come together with just the right amount of approximation to promote good healing and prevent leakage and formation of false lumens. If the incised edges are too far apart scarring will occur causing restrictions. The walls cannot be compressed tightly between two hard surfaces which will damage the vessels. The prior art teaches plumbing-like fittings clamped onto vascular structures. However, clamping and compressing the vessel walls too tightly will cause necrosis of the vessel between the clamps. If necrosis occurs the dead tissue will become weak and most likely cause a failure of the joint. Still further Such rings and tubes used to clamp vessels together do not follow the correct anatomical contours to create an unrestricted anastomosis. Failing to account for the way healing of this type of junction occurs, and not accounting for the actual situation may cause a poor result.
A suture technique has the advantage of having the surgeon making on-the-fly decisions to add an extra suture if needed to stop a leak in the anastomosis. In a mechanical minimally invasive system it will not be possible to put in an ‘extra suture throw’ so the system must provide a way to assure complete hemostasis. Approximation using a mechanical system will not be perfect. If the design errs on the side of not over-compressing the tissue, there may be very small areas that may present a leak between the edges of the vessel walls. Healing with prior art techniques using mechanical joining means is not as efficient as it could be. There is a need for an anastomotic technique that accounts for the way healing actually occurs and provides proper structural support during the healing process.
Many times when a CABG operation is undertaken, the patient has multiple clogged arteries. At the present time, the average number of grafts is 3.5 per operation. When multiple grafts are performed, there is sometimes the opportunity to use an existing or newly added supply vessel or conduit for more than one bypass graft. This is known as a jump graft, whereby the conduit, at the distal end thereof is terminated in a side-to-side anastomosis first, with an additional length of conduit left beyond the first junction. Then, an end of the conduit is terminated in an end-to-end junction. This saves time and resources and may be necessary if only short sections or a limited amount of host graft material is available.
Conventional means and methods of performing an anastomosis do not permit the formation of multiple anastomotic sites on a single graft vessel such as at both proximal and distal ends. Thus a surgeon will have to use multiple tools to perform multiple anastomoses. This will be either impossible or very expensive. Therefore, there is a need for a means and a method for performing an anastomosis which will lend itself to efficient and cost-effective multiple by-pass techniques.
There is also a need for a means and method for performing an anastomosis which will lend itself to efficient and cost-effective jump graft techniques.
As noted above, performing anastomosis in a minimally invasive manner while the patient's heart is beating requires an extremely high degree of dexterity. Any apparatus used in such a procedure must therefore be as easy and efficient to use as possible so that a surgeon can focus most of his or her attention on the anastomosis site.
Further, any apparatus used for anastomosis without hand-suturing should be amenable to efficient manufacture.
U.S. Pat. No. 5,868,763, issued Feb. 9, 1999, teaches methods and apparatus for accomplishing anastomosis without hand-suturing in a manner overcoming many of the disadvantages of conventional anastomosis methods and apparatus such as those described above. The apparatus of U.S. Pat. No. 5,868,763 includes a flexible “cuff” having tines configured to pierce a vessel or other organ (e.g., to penetrate tissue around the edges of an incision in the side-wall of a blood vessel) to attach the cuff to the vessel or organ. When deformed, the cuff remains in the deformed configuration until physically moved into another configuration. The cuff can be mounted to a vessel (or other organ) around an incision, and then deformed to open or close the incision as desired.
When implementing side-to-side anastomosis (to attach the side wall of one vessel to the side wall of another vessel), one cuff is attached around an incision in the side wall of the first vessel and another cuff is typically attached around an incision in the side wall of the other vessel. The cuffs are then aligned and fastened together. However, the cuffs are designed (and attached to the vessels) such that when the two cuffs are aligned, the incised tissue edges of the two vessels are placed in edge-to-edge contact (so that there is a risk that the anastomosis will be completed without the intima of the two vessels being in direct contact with each other at all locations where the vessels meet each other).
In embodiments in which a single cuff is used to implement side-to-side anastomosis, the cuff is attached (by a first set of times) around an incision in the side wall of one vessel, the cuff is aligned with an incision in the side wall of a second vessel, and the cuff is attached to the second vessel (by a second set of times extending around the second vessel). However, the cuff is designed (and attached to the first vessel) such that when the cuff is aligned with the second vessel, the incised tissue edges of the two vessels are placed in edge-to-edge contact (so that there is a risk that the anastomosis will be completed without achieving direct intima-to-intima contact at all locations where the vessels meet each other).
FIG. 4 shows a side-to-side anastomosis which connects vessel 10 to vessel 12, as implemented by two cuffs 40 and 45 of the type described in U.S. Pat. No. 5,868,763. Cuff 40 has an oval shaped (the oval extending in a horizontal plane perpendicular to the plane of FIG. 4), flexible metal body 41 having tines 42. Sheet 98 (which is preferably made of woven fabric suitable for use in surgery) is attached to the metal body. A generally oval opening extends through metal body 41 and sheet 98, so that cuff 40 can be attached around an incision in vessel 10 with the opening providing access to the incision.
Similarly, cuff 45 has an oval shaped, flexible metal body 43 having tines 44. Sheet 99 (preferably made of woven fabric suitable for use in surgery) is attached to metal body 43. A generally oval opening extends through body 43 and sheet 99, so that cuff 45 can be attached around an incision in the side wall of vessel 12 with the opening providing access to the incision.
To perform the anastomosis shown in FIG. 4, an anvil (not shown) is inserted through an incision in artery 10, and cuff 40 (with each of the tines 42 in a straight configuration) is positioned in the incision with the sharp tips of tines 42 engaging the tissue surrounding the incision. An installing instrument (not shown) is then operated to force the tines 42 against the anvil, thus causing the tines 42 to penetrate through the tissue into contact with the anvil and to bend into the bent configuration shown in FIG. 4 (so as to attach cuff 40 to the tissue of artery 10 surrounding the incision). An anvil (not shown) is also inserted through an incision in artery 12, and cuff 45 (with each of the tines 44 in a straight configuration) is positioned in the incision with the sharp tips of tines 44 engaging the tissue surrounding the incision. A cuff-installing instrument (not shown) is then operated to force tines 44 against the anvil, thus causing tines 44 to penetrate through the tissue into contact with the anvil and to bend into the bent configuration shown in FIG. 4 (so as to attach cuff 45 to the tissue of artery 12 surrounding the incision). Then, cuff 40 is aligned with cuff 45, and body 98 of cuff 40 is attached to body 99 of cuff 45 by fasteners 114 (as shown in FIG. 4).
When cuffs 40 and 45 are so aligned, the incised tissue edges of vessels 10 and 12 are placed in edge-to-edge contact at locations “A.” There is some risk that the intima of vessels 10 and 12 (the very thin tissue layer lining the inner diameter of each vessel) may not be placed in direct contact with each other at all locations where the vessels meet each other. For example, there may be a gap where the central portion of one incised tissue edge (rather than the thin intima at the inner end of the edge) comes into direct contact with the central portion of the other incised tissue edge. Since the intima tissue provides lubricity and a low friction surface against which blood can flow, failure to accomplish uniform intima-to-intima contact between the two vessels has several disadvantages, including the following: blood flowing from one joined vessel to the other may encounter a “gap” in the intima layer to which it is exposed (a hole in an otherwise continuous intima layer at which intima tissue is missing) so that the blood comes into direct contact with the tissue that is normally shielded from the blood by intima tissue. If this occurs, the flowing blood can create a false lumen by separating tissue layers of one or both of the vessels, or the flowing blood can otherwise cause damage at the anastomosis site which hinders healing or results in leakage.
In addition to achieving the noted advantages of direct intima-to-intima contact (relative to “incised edge”-to-“incised edge” contact as in FIG. 4), the present invention also allows the elimination of hemostatic media (e.g., bodies 98 and 99) from rings which are employed to facilitate anastomosis. Thus, in contrast with the FIG. 4 apparatus (in which fabric bodies 98 and 99 line the outer sidewalls of the joined vessels 10 and 12), the invention facilitates anastomosis with direct intima-to-intima contact, without hand-suturing, and without provision of hemostatic media for pressing against the joined vessels at the anastomosis site.
The present invention, like the apparatus disclosed in U.S. Pat. No. 5,868,763, can be used to perform end-to-end anastomosis (in which the open end of one vessel is attached to the open end of another vessel, for example, with vessel geometry as in FIG. 3) or end-to-side anastomosis (in which the open end of one vessel is attached in fluid communication with an incision in the side wall of another vessel), as well as side-to-side anastomosis (with vessel geometry as in FIGS. 1 and 4). However, unlike the apparatus disclosed in U.S. Pat. No. 5,868,763, the apparatus of the present invention allows direct and uniform intima-to-intima contact to be achieved in all three cases.